The invention relates to a controller for an internal combustion engine, particularly to a controller for an internal combustion engine for controlling a restart of the internal combustion engine for an idling stop.
In recent years, for purposes of decreasing a fuel consumption and an amount of an exhaust gas of the internal combustion engine, a number of automobiles in which the idling stop is performed increases. For performing the idling stop, various techniques for stopping automatically the internal combustion engine when the internal combustion engine is in an idling condition during a stoppage of the automobile, and subsequently restarting automatically the internal combustion engine for start moving, have been proposed.
In the idling stop, if a time period for restarting the internal combustion engine is long, the start of movement of the automobile is delayed in comparison with a driver's intension for the start moving to deteriorate a drivability. Therefore, in an idling stop control, it is important for the internal combustion engine to be restarted quickly and smoothly.
Further, in an idling stop system for restarting the internal combustion engine by cranking the internal combustion engine up with a starter motor or the like, a great amount of electric power is required for the cranking up to cause a provability of that a lack in electric power of a battery electric power source occurs to prevent temporarily an electric load from being activated when restarting. Further, a load to the battery is great to accelerate a deterioration of the battery.
Therefore, for a multi-cylinder 4-cycle direct-injection spark-ignition engine, a restarting method in which a fuel is injected in a cylinder in expansion stroke when the internal combustion engine is stopped, and the ignition is performed after the fuel injection to utilize a rotational torque generated by a combustion, is proposed.
However, in a prior art disclosed by JP-A-11-125136, a reduction in exhaust gas on the restarting for satisfying emission regulations tightened year after year is not considered.
For an improvement in exhaust gas characteristic on the restarting of the internal combustion engine, a control method in which an air-fuel ratio is made rich temporarily on the restating to prevent a deterioration in exhaust gas, particularly in NOx on the restarting of the internal combustion engine in an air fuel ratio control device of the internal combustion engine, is proposed (by, for example, JP-A-2000-104588).